The invention relates to the field of steam engines which can be operated using a steam power process and which are connected to an internal combustion engine.
In the development of internal combustion engines, the reduction of fuel consumption is of high importance. Internal combustion engines convert the energy of the fuel into mechanical energy for driving vehicles. Here, a large proportion of the energy is released as waste heat which is dissipated by the cooling system or conducted away from the internal combustion engine in the exhaust gas. To utilize said energy, it is conceivable for the internal combustion engine to be coupled to a steam power process. Here, the heat energy from the internal combustion engine is used to generate steam, which is expanded in an expansion machine and thus provides further energy which can be utilized for driving the vehicle.
The combination of an internal combustion engine with a steam engine for waste heat utilization is particularly suitable for a utility vehicle because, here, the internal combustion engine must output a large amount of power, and therefore a large amount of heat energy is available for steam generation.
For the connection of the steam engine to the internal combustion engine, it is conceivable for a rigid coupling to be provided. This means, however, that the internal combustion engine carries the steam engine along already from the time at which said internal combustion engine is started, even though sufficient steam pressure for the steam engine is not yet available. This yields the disadvantage that, specifically during the starting of the internal combustion engine, the efficiency of the overall system is decreased corresponding to the friction of the steam engine. However, in this way, the steam engine can be set in motion by the internal combustion engine by being carried along, such that the steam engine does not remain stationary in an unfavorable position in which it possibly cannot start up of its own accord.
It is also conceivable for the steam engine and the internal combustion engine to be connected to one another via an interposed freewheel. In this way, the internal combustion engine can rotate freely when sufficient steam pressure for the steam engine is not available. In this situation, therefore, the internal combustion engine need not impart the additional power lost through friction of the steam engine. Here, however, there is the disadvantage that the internal combustion engine no longer sets the steam engine in motion by carrying the latter along, as a result of which, in the case of unfavorable standstill positions of the steam engine, depending on the design thereof, said steam engine can possibly no longer start up of its own accord.